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Circles — quick quiz

5 real IOQM questions on Circles. Instant scoring and solutions, no signup — see where you stand in ~3 minutes.

Question 1 of 2

HARD

Two circles of radii 5 and 12 are externally tangent to each other. A third circle is tangent to both and also tangent to their common external tangent line. Find the radius of the third circle.